TimeSeries support

ObjectBox core comes with time-series support - consider exposing in Dart. Basic characteristics:

• there's an "id-companion" annotation for a millisecond or nanosecond-precision time field (OBXPropertyFlags_ID_COMPANION)
• box (or some extension of it) - have a getter for global (obx_box_ts_min_max) and local (obx_box_ts_min_max_range) "extremes", i.e. minimum/maximum time value and object (id)
• add an option to link based on the time field value (obx_qb_link_time) - linking using a time range or a single value
• time-series support is a "feature" (similar to sync) and may not be available in every library build variant (doesn't apply to the annotation - those will always be accepted) - this influences the APIs but also how to distribute the TS-enabled variant of a library, e.g. for Android, iOS, where we depend directly on objectbox-android and objectbox-swift projects, respectively.

Start by reviewing the existing Dart bindings and the ObjectBox core time-series APIs named in the issue, including the annotation, extremes, and time-based linking entry points. Confirm how optional library build variants are distributed for Android and iOS; done means these capabilities are exposed consistently while annotation support remains available in every variant.